Role of the Thyroid
The thyroid is a butterfly-shaped organ located just below the Adam’s apple in the neck. Made up of small sacs, this gland is filled with an iodine-rich protein called thyroglobulin along with the thyroid hormones thyroxine (T4) and small amounts of triiodothyronine (T3).
The primary function of these two hormones is to regulate metabolism by controlling the rate at which the body converts oxygen and calories to energy. In fact, the metabolic rate of every cell in the body is regulated by thyroid hormones, primarily T3.7
In healthy individuals the gland is imperceptible to the touch. A visibly enlarged thyroid gland is referred to as a goiter. Historically, goiter was most frequently caused by a lack of dietary iodine.8 However, in countries where salt is iodized, goiter of iodine deficiency is rare.